chemical analysis Flashcards
calcium (Ca2+) flame test result
orange-red flame
copper (Cu2+) flame test result
green flame
sodium (Na+) flame test result
yellow/orange
potassium (K+) flame test result
lilac flame
lithium (Li+) flame test result
crimson flame
what do group 3 metal ions do when reacted with sodium hydroxide
form a white precipitate that redissolves in excess sodium hydroxide
what colour precipitate do group 1 and 2 metal ions form when reacted with sodium hydroxide
white precipitate
what colour precipitate does iron (II) form?
green precipitate
what colour precipitate does iron (III) form?
brown precipitate
what colour precipitate does copper (II) form?
blue precipitate
what are the products of reactions between a carbonate and a dilute acid
a salt
water
carbon dioxide
how do you test for halide ions?
add dilute nitric acid
then add silver nitrate
what halide ion forms a yellow precipitate
iodide
what halide ion forms a white precipitate
chloride ions
what colour precipitate does bromide ions form?
cream
what is the method for testing for sulfate ions?
acidify with dilute hydrochloric acid
add barium chloride
what forms if sulfate ions are present?
a white precipitate
why do we add nitric acid when testing for halides?
the nitric acid removes any carbonates,
stopping a precipitate forming with the silver added after
what are the advantages and disadvantages of using instrumental methods in chemical analysis?
advantages:
greater sensitivity and accuracy
faster results
able to analyse smaller/ tiny samples
disadvantages:
instruments are often expensive
special training is required to operate the instruments
results are often only useful when compared to a known substance
what is the method for flame emission spectroscopy? (2steps)
1)place a sample of the metal in a flame, light will be given off
2) light given off is captured by a spectroscope, the spectroscope produces a line spectrum by differentiating the different wavelengths
what is the output of a spectroscope?
a line spectra
what can we use flame emission spectroscopy to investigate?
what metal ions are present
what concentrations the ions are in
what do impurities do to the boiling point of a substance?
increase the boiling point and increase the range at which the substance boils
